An idea has conventionally been proposed in which vehicles running on a road and the like form a group such as to construct an array also known as platoon. Running in a group is expected to be effective in improving mileage and traffic flow efficiency, alleviating driving load, increasing moving speed, and so forth. Known as an apparatus for forming such a vehicle group is one computing a degree of similarity between vehicle information of a vehicle and vehicle information of another vehicle or vehicle group and forming a group with a vehicle or vehicle group whose similarity is at a set value or greater (see, for example, Japanese Patent Application Laid-Open No. 10-261195). This apparatus uses destinations, vehicle position information, engine output, torque characteristics, acceleration performances, brake characteristics, and the like as vehicle information to be compared between the vehicles.